ERAAP substrate Ep – Fluorescent Peptides

Ep is a peptide-based fluorescent probe that can detect the intracellular amino-peptidase- ER aminopeptidase associated with antigen processing (ERAAP). ERAAP cleaves peptides presented by major histocompatibility complex (MHC) class I molecules to determine which are displayed on cell surfaces for T cell recognition. Down-regulation of ERAAP alters these cell surface peptides resulting in the cell being recognised as foreign. Therefore ERAAP is a potential target for increasing the immune response towards tumours. Down-regulation of ERAAP is also implicated in auto-immunity. Ep contains the fluorescent dye BODIPY and the fluorescent quencher dinitrophenyl (DNP), conjugated to the KK-SIINFECL peptide which is based on a known ERAAP-substrate. Ep initially has low fluorescence due to the proximity of the DNP quencher, however after ERAAP cleaves the N-terminal amino acid of Ep and releases the DNP quencher, a dramatic 20 fold increase in fluorescence is seen. Ep can detect ERAAP in cells in a highly sensitive and specific manner. Ep can detect ERAAP activity in live cells and in high-throughput-screens (HTS), and can compete with endogenous cellular substrates for ERAAP.

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